CVE-2019-5441 in App Extract
Summary
by MITRE
An OS Command Injection has been discovered in the Nextcloud App: Extract prior to version 1.2.0.
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Analysis
by VulDB Data Team • 10/03/2023
The vulnerability identified as CVE-2019-5441 represents a critical operating system command injection flaw within the Nextcloud Extract application, a widely used file extraction utility that allows users to decompress archived files directly within the Nextcloud platform. This vulnerability specifically affects versions prior to 1.2.0 and stems from inadequate input validation mechanisms within the application's file processing pipeline, creating a pathway for malicious actors to execute arbitrary commands on the underlying operating system. The flaw resides in how the application handles user-supplied archive filenames and extraction parameters, particularly when processing compressed files that contain specially crafted filenames or directory traversal sequences. Attackers can exploit this vulnerability by uploading maliciously formatted archive files or manipulating extraction parameters to inject OS commands that will be executed with the privileges of the Nextcloud service account, potentially leading to complete system compromise.
The technical exploitation of this vulnerability aligns with CWE-77, which classifies command injection flaws as weaknesses that occur when an application incorporates untrusted data into operating system commands without proper sanitization or validation. The vulnerability demonstrates characteristics of CWE-88, where command-line arguments are constructed using user-supplied input that is not properly escaped or quoted, and CWE-94, which covers the execution of arbitrary code through improper input handling in interpreted environments. The attack vector typically involves uploading a malicious archive file containing specially crafted filenames or directory traversal sequences that bypass normal validation checks, allowing attackers to inject shell commands that execute during the extraction process. This type of vulnerability is particularly dangerous in web-based file management systems where the application typically runs with elevated privileges to perform file operations, creating a direct bridge between user input and system command execution.
The operational impact of CVE-2019-5441 extends beyond simple data theft or service disruption, as successful exploitation can lead to complete system compromise and persistent access within the target environment. An attacker who successfully exploits this vulnerability can execute commands with the privileges of the Nextcloud service account, potentially gaining access to sensitive data stored within the Nextcloud instance, accessing other services running on the same host, or establishing backdoors for continued access. The vulnerability is particularly concerning in enterprise environments where Nextcloud servers often serve as central file repositories containing confidential business data, intellectual property, and personal information. Additionally, the attack surface is broad as the vulnerability affects any Nextcloud deployment using the Extract app prior to version 1.2.0, making it a significant risk for organizations that have not yet applied the necessary security patches. The vulnerability also provides potential for lateral movement within networks, as compromised Nextcloud servers may have access to other systems or services within the same infrastructure.
Organizations affected by CVE-2019-5441 should immediately implement the security patch released by Nextcloud in version 1.2.0, which addresses the input validation issues by properly sanitizing user-supplied filenames and implementing proper command escaping mechanisms. System administrators should also conduct comprehensive vulnerability assessments to identify all instances of the vulnerable Extract app across their infrastructure and ensure proper network segmentation to limit potential damage from successful exploitation attempts. The mitigation strategy should include monitoring for suspicious file upload activities and implementing proper access controls to restrict who can upload and extract files within the Nextcloud environment. Organizations should also consider implementing additional security controls such as web application firewalls to detect and block malicious command injection attempts, and establish robust incident response procedures to quickly identify and remediate any potential exploitation attempts. The vulnerability serves as a reminder of the critical importance of keeping third-party applications updated and maintaining proper input validation controls throughout all application components, particularly those handling user-supplied data in contexts where system-level operations are performed.